Coordinative assembly

Peptidases encoded by many viruses play essential roles at various stages of viral replication, including the coordinated assembly and maturation of virons [7a]. Viral peptidases have become important drug targets in the treatment of viral infections. Of note are inhibitors of proteases of the human immunodeficiency virus (HIV), particularly HIV-1 protease (HIV-1 retropepsin, EC 3.4.23.16) and HIV-2 protease [47-50], Drugs in this class, which include indinavir, ritonavir, and saquinavir, are useful in the treatment of AIDS, especially when administered as a cocktail together with one of the drugs that act on the viral retrotranscriptase (e.g., didanosine, stavudine, and zidovudine (AZT)). 

Konarev DV, Khasanov SS, Saito G, Otsuka A, Lyubovskaya RN (2007) Ionic and neutral Cgo complexes with coordination assemblies of metal tetraphenylporphyrins, M°TPP2-DMP (M = Mn, Zn). coexistence of (Ceo /z dimers bonded by one and two single bonds in the same compound. Inorg Chem 46 7601-7609... 

According to X-ray diffraction data, in the solid-state complex 87 adopts a six-membered metallacyclic structure, as the result of P-Pd-Cl-B bridging coordination. The interaction of the borane moiety with the chlorine atom is apparent from the short Cl-B distance (2.165(2) A) and the pyramidalization of the boron environment (EBa = 349.1°). The bridging coordination of the Pd-Cl bond by the PB 7b contrasts with the B-pendant coordination mode adopted by complex 72, deriving from the related ligand 7e featuring mesityl groups at boron (see Section IV.A). This illustrates the role of steric factors in the participation, or not, of the Lewis acid in the coordination assembly. 

In order to answer some of these outstanding questions, this chapter presents and analyzes a variety of chiral architectures based on metal-ligand coordinative interactions. Although there are a number of ways in which chirality can be introduced into coordination assemblies [2], we will concentrate on ensembles formed from achiral components, where chirality arises from metal coordination geometries or asymmetric ligand arrangements. Particular focus lies with assemblies that show host-guest encapsulation potential and maintain their chirality in solution. 

Fig. 27 Representation of the N-heterocyclic ligands 40, 41 and 42 that form cationic Co4L6 tetrahedra. The identical coordination assemblies are illustrated by the distorted tetrahedron Co4406 (43). Reprinted with permission from [150], Copyright 2004 The Royal Society of Chemistry...

An interesting ferrocene-bridged zinc porphyrin macrocycle was synthesized by Shoji et al. [146], This group succeeded in visualizing a single molecule of a supramolecular coordination assembly on Au(lll) in UHV [147], The discrete... 

Fujita M, Tominaga M, Hori A, Therrien B (2005) Coordination assemblies from a Pd(II)-comered square complex. Acc Chem Res 38 371-380... 

Linares F, Galindo MA, Galli S, Angustias Romero M, Navarro JAR, Barea E (2009) Tetranuclear coordination assemblies based on half-sandwich ruthenium(II) complexes noncovalent binding to DNA and cytotoxicity. Inorg Chem 48 7413-7420... 

Coordinates assembly and delivery of medical equipment and supplies. 

In a subsequent study, the Co coordinated assembly was grafted onto a cross-linked poly(glycidoxypropylmethacrylate) (GMA)-ethylene glycol dimethacrylate (EDMA) support surface. The template and Co ions were then leached out from the matrix. This surface grafted polymer exhibited turnover, Michaelis-Menten kinetics and mechanisms such as inhibition by tosyl phenyl alanyl chloromethyl ketone and inhibition on acetylation of hydroxyl group of 2-hydroxyethylmethacry-late (HEMA), similar to native chymotrypsin. 

The various protein complexes are coordinately assembled and steady-state biogenesis takes over. 

As already mentioned, the supramolecular structure of coordination assemblies is ruled by geometric factors, such as the metal coordination environment and, in particular, the number and geometry of coordination sites available for the interaction with organic building blocks. 

Fujita, M., Tominaga, M., Hori, A. and Therrien, B., Coordination assemblies from a Pd(II)-cornered square... 

To obtain discrete 3D coordination assemblies, molecular panels should be linked with an appropriate structural turn (e.g., 90°) and, thus, the use of cis coordination cites of transition metals are effective to provide such turns in the assembled structures. In this regard, cis-protected Pd(II) block 1, which was developed in our laboratories ten years ago, is a useful metal component which makes possible the design of simple self-assembly from non-sophisti-cated ligands (e.g., 4-pyridyl-functionalized molecular panels). 

Table 1. Examples of typical ID bridging ligands with two linking sites and their 2D coordination assemblies... 

Three-dimensional coordination assemblies using precisely designed bridging ligands with more than two linking sites are discussed by Saalfrank in the preceding chapter of this volume [15],... 

Triangles are the simplest 2D units and are components of a family of polyhedrons. Thus we first discuss the assembly of triangles. One of the simplest triangular molecular panels is 2,4,6-tris(4-pyridyl)-l,3,5-triazine (2), which has been employed frequently for infinite coordination assemblies by Robson [9,16],... 

Following the triangular molecular panels, use of square and rectangular molecules as building blocks for three-dimensional coordination assemblies is discussed in this section. 

Bidentate pyrazolyl-based ligands have shown to be versatile building blocks for the synthesis of a plethora of coordination assemblies. Initial work by McCleverty and Ward in the late 1990s showed that the synthesis of cages [Co4(L )6CX](X)7 (where L and = bidentate pyrazolyl-pyridine ligands ... 

Pyridyl ligands are certainly candidates for forming stable self-complementary coordination assemblies and are conventionally employed for supramolecular structure formation. Zn and Mg complexes of meso- and b-pyr-role-substituted 2-pyridylporphyrins (4a-c) were therefore prepared [37,38]. Crystallographic analysis was used to verify that the required slipped cofacial arrangement had been generated, and demonstrated the overlapping of one of the pyrrolic rings in each porphyrin. This confirmed the structural similarity between the sample and the special pair. The stability constant was reported to be 5 x 10 for the Mg dimer of the meso-pyridyl case 4b. 

M. Fujita, M. Tominaga, A. Hori, B. Therrien, Coordination assemblies from a Pd(ll)-comered square complex, Acc. Chem. Res., 2005, 38, 371. 

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